1. Field of the Invention
This invention relates to the monitoring of a subsea flow device, such as the monitoring of the temperature of a subsea flow line used in the production of fluids from a hydrocarbon reservoir, and the powering of such a monitoring operation.
2. Description of Related Art
In the production of fluids from a subsea hydrocarbon reservoir, a variety of subsea flow devices are typically used, such as a pipeline or flowline that is disposed on the seafloor and provides a passage through which the fluids be communicated. For example, a subsea well can provide produced fluids from the subsea reservoir to a subsea flowline that carries the fluids away from the well. The flowline can carry the fluids to an on-shore facility, other subsea equipment, a riser that carries the fluid to a topside facility, or the like. Other subsea flow devices can include flow storage, actuation, or control equipment, such as tanks, pumps, motors, valves, and the like.
The monitoring of such subsea flow devices can be important to achieving successful and optimal production from the well. For example, subsea flowlines that carry high temperature fluids can be exposed to severe temperature gradients and variations, especially for flowlines that operate in deep water. Even for insulated flowlines, high thermal gradients can result between the inside and outside of the flowline by virtue of the difference in temperature of the produced fluids inside the flowline and the seawater outside the flowline. Temperature variations over time can result from changes in the flow of the produced fluid, such as between times of production when the presence of the produced fluid can heat the pipe, and times of no production when the pipe is either empty of produced fluid or contains produced fluid that cools when it does not flow. The thermal effects on the pipeline can include stress, strain, and movement of the pipeline on the seafloor. In some cases, such effects can threaten the integrity of the flowline.
A subsea flowline can be monitored in an effort to assess the ongoing integrity of the flowline and thereby facilitate planned preventative measures and avoid unplanned interventions for unforeseen events, such as unplanned interruption of production. One conventional monitoring method includes performing periodic visual inspections of the flowlines using a Remotely Operated Vehicle (ROV) that can travel along the flowline and gather information with a camera. Alternatively, an in-place monitoring system can be installed on the flowline. The system can include multiple transducers that detect thermal or other data from a plurality of locations along the flowline, and the transducers can communicate the data via a fiber optic cable that extends along the flowline to a receiver. In some cases, the transducers can be powered by the thermal differential that exists between the flowline and the surrounding seawater. While the monitoring system could potentially provide more information than a visual inspection, such systems can be complex, expensive, and unreliable, e.g., because the fiber optic cable can break. Further, the installation of the system can be incompatible with some types of flowlines and certain flowline deployment techniques, and can increase the cost of providing, deploying, and maintaining the flowline.
A continued need exists for an improved system, apparatus, and method for monitoring a subsea flow device, such for monitoring the temperature or other characteristics along a flowline that is disposed on the seafloor and carries hot produced fluid in an environment of cold sea water. The system, apparatus, and method should be compatible with different types of deployment and provide reliable monitoring of the flow device.